A producing well will have a wellhead or Christmas tree at the surface for controlling the well. The wellhead assembly supports casing which extends into the well. Tubing extends through the casing for producing the formation fluids. The Christmas tree is a tubular body having a bore extending vertically through it with outlets leading from the bore through the sidewall. Valves are mounted in the bore and to the outlets of the tree for providing access to the tubing as well as directing the produced fluid out to a flow line.
Current wellhead technology on shallow gas wells utilizes Demco style gate valves which were originally designed for use on mud lines on the surface of a drilling rig. They are not readily field serviceable, primarily because they were not intended for use in a wellhead.
Current wellhead technology for shallow gas wells does not provide the capability of hanging a coil tubing string below an existing wellhead. The existing wellhead is decommissioned in place, and the secondary string or coil tubing string is suspended from above the existing master valve. Accordingly, secondary well control is needed as well as a new wellhead above the current master valve.
There is a need in the art for a wellhead valve that mitigates the difficulties of the prior art.